<div class="refentry" lang="en" xml:lang="en"><a id="glClipPlane"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glClipPlane — specify a plane against which all geometry is clipped</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table><tr><td><code class="funcdef">void <b class="fsfunc">glClipPlane</b>(</code></td><td>GLenum  </td><td><var class="pdparam">plane</var>, </td></tr><tr><td> </td><td>const GLdouble *  </td><td><var class="pdparam">equation</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>plane</code></em></span></dt><dd><p>

Specifies which clipping plane is being positioned.

Symbolic names of the form <code class="constant">GL_CLIP_PLANE</code><span class="emphasis"><em>i</em></span>,

where <span class="emphasis"><em>i</em></span> is an integer between 0 and <code class="constant">GL_MAX_CLIP_PLANES</code>

<math overflow="scroll">

<mn>-1</mn>

</math>,

are accepted.

</p></dd><dt><span class="term"><em class="parameter"><code>equation</code></em></span></dt><dd><p>

Specifies the address of an array of four double-precision floating-point values.

These values are interpreted as a plane equation.

</p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>

Geometry is always clipped against the boundaries of a six-plane frustum

in <span class="emphasis"><em>x</em></span>, <span class="emphasis"><em>y</em></span>, and <span class="emphasis"><em>z</em></span>.

<code class="function">glClipPlane</code> allows the specification of additional planes,

not necessarily perpendicular to the <span class="emphasis"><em>x</em></span>, <span class="emphasis"><em>y</em></span>, or <span class="emphasis"><em>z</em></span> axis,

against which all geometry is clipped.

To determine the maximum number of additional clipping planes, call

<a class="citerefentry" href="glGetIntegerv"><span class="citerefentry"><span class="refentrytitle">glGetIntegerv</span></span></a> with argument <code class="constant">GL_MAX_CLIP_PLANES</code>. All

implementations support at least six such clipping planes.

Because the resulting clipping region is the intersection

of the defined half-spaces,

it is always convex.

</p><p>

<code class="function">glClipPlane</code> specifies a half-space using a four-component plane equation.

When <code class="function">glClipPlane</code> is called,

<em class="parameter"><code>equation</code></em> is transformed by the inverse of the modelview matrix

and stored in the resulting eye coordinates.

Subsequent changes to the modelview matrix have no effect on the

stored plane-equation components.

If the dot product of the eye coordinates of a vertex with the

stored plane equation components is positive or zero,

the vertex is <span class="emphasis"><em>in</em></span> with respect to that clipping plane.

Otherwise, it is <span class="emphasis"><em>out</em></span>.

</p><p>

To enable and disable clipping planes, call

<a class="citerefentry" href="glEnable"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> and <a class="citerefentry" href="glDisable"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a> with the argument

<code class="constant">GL_CLIP_PLANE</code><span class="emphasis"><em>i</em></span>,

where <span class="emphasis"><em>i</em></span> is the plane number.

</p><p>

All clipping planes are initially defined as (0, 0, 0, 0) in eye coordinates

and are

disabled.

</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>

It is always the case that <code class="constant">GL_CLIP_PLANE</code>

<math overflow="scroll"><mi mathvariant="italic">i</mi></math>

= <code class="constant">GL_CLIP_PLANE0</code> +

<math overflow="scroll"><mi mathvariant="italic">i</mi></math>.

</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>

<code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>plane</code></em> is not an accepted value.

</p><p>

<code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glClipPlane</code>

is executed between the execution of <a class="citerefentry" href="glBegin"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>

and the corresponding execution of <a class="citerefentry" href="glEnd"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.

</p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>

<a class="citerefentry" href="glGetClipPlane"><span class="citerefentry"><span class="refentrytitle">glGetClipPlane</span></span></a>

</p><p>

<a class="citerefentry" href="glIsEnabled"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_CLIP_PLANE</code><span class="emphasis"><em>i</em></span>

</p></div>

{$pipelinestall}{$examples}

<div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>

<a class="citerefentry" href="glEnable"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a>

</p></div><div class="refsect1" lang="en" xml:lang="en"><div id="Copyright"><h2>Copyright</h2><p>

Copyright © 1991-2006

Silicon Graphics, Inc. This document is licensed under the SGI

Free Software B License. For details, see

<a class="ulink" href="https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/" target="_top">https://web.archive.org/web/20171022161616/http://oss.sgi.com/projects/FreeB/</a>.

</p></div></div></div>